<p>A cooling fan (10) for a vehicle engine (50), comprising a fan casing (60) and a fan rotor (12) which is movable axially relative to the fan casing during operation. According to the invention there is an actuator (20) for moving the fan rotor (12) to positions which represent various degrees of protrusion (a) from an end of the fan casing (60) in order to optimise the fan's suction capacity and efficiency on the basis of current operating parameters such as fan speed and vehicle velocity.</p>
